1. Field of the Invention
The present invention relates to a heat developable silver halide color photographic light-sensitive material and to a method of forming colored images. To be more specific, it relates to a heat developable silver halide color photographic light-sensitive material which does little harm to the environment, and is suitable for simple and rapid image formation. What is more, it relates to a silver halide color photographic light-sensitive material, having a high speed of sensitivity and low fogging. Also the present invention relates to a simple and rapid process of forming colored images by using said heat developable silver halide color photographic light-sensitive material, in which process the environment is not adversely affected and the finished prints can have low fogging.
2. Description of the Related Art
Over the past few years light-sensitive materials which use silver halides for color photography have developed so much that now it is very easy to get high quality color images. For example, in what is usually called the color photographic method, color negatives are used for camera use, and after development the image information recorded on the negatives is optically printed onto color photographic paper to give the color prints.
In recent years this process has developed to a high level and large amounts of color printing can be produced on a large scale efficiently. Compact and simple printing processers set up in color printing labs or shops (the so called mini-labs) make color photography easy and fun for all.
The color photography now in common use reproduces color by the subtractive color process. Generally, a color negative film comprises a transmittable support and light-sensitive layers thereon utilizing a silver halide emulsion as a light-sensitive component having a sensitivity to the blue, green or red wavelength region of the spectrum, and a so-called color coupler capable of producing a yellow, magenta or cyan dye as a complementary hue of the sensitive wavelength region of the respective layers. A color negative film which has been exposed imagewise, is developed in a color developer containing an aromatic primary amine developing agent. In this process, the developing agent develops, i.e., reduces the exposed silver halide grains and the oxidation product of the developing agent formed during the foregoing reduction, and undergoes a coupling-reaction with the color coupler to form a dye. The silver (developed silver) generated by the color development and the unreacted (unexposed) silver halide are removed by means of a bleaching and fixing process. This creates an image on the color negative film. Consequently, color photographic paper which comprises a reflective support and light-sensitive layers formed thereon having the same combinations of light-sensitive wavelength region and hue to be produced as in the color negative film, is subjected to exposure through the developed negative film, and color-developing, bleaching and fixing the color photographic paper in the same manner as in the case of the negative film to obtain a color print having a color image as a reproduction of an original image thereon.
Although these systems are widely adopted at the moment, there is a growing demand for a simpler system. The first reason for this is that expertise and skilled operators are necessary due to the requirement of strict control of the composition and the temperature of the processing solution in a processing bath for the above procedure composed of color development, bleaching and fixing. The second reason for this is that closed equipment used exclusively in the developing process is often required, due to substances, such as a developing agent and, as a bleaching agent, an iron chelate compound, the discharge of which is regulated from the standpoint of environmental protection, contained in the processing solution. The third reason for this is that the currently available system does not perfectly fulfill the requirements for rapid reproduction of images, as the above developing process still requires a long time.
In recent years many technical improvements have been presented as a result of this background. Many techniques involving the use of emulsions containing high levels of silver chloride have been presented with the specific aim of developing simple and rapid developing processes. By using such emulsions, advantages like speeding up development, and increasing the re-usability of the processing solutions can be realized. Because of this, the majority of printing light-sensitive materials in use today are printing light-sensitive materials, such as color photographic paper, using such emulsions.
U.S. Pat. Nos. 5,264,337, No. 5,292,632, No. 5,310,635, and WO 94/22054 and others disclose the use of an emulsion having a high content of silver chloride tabular grains, made up of a (100) plane, in a color photographic light-sensitive material as a technique utilizing an emulsion having a high content of silver chloride to a photographic light-sensitive material for the purpose of speeding up the developing process. These techniques obtain high speed development through the use of high level silver chloride emulsions. Also there are such advantages as being able to use the same processing solution for both photographic light-sensitive materials and for printing light-sensitive materials. However, development processing with processing solutions has always been necessary which is environmental problem.
On the other hand, as attempts different from these, a simpler system which does not utilize the developing agent and bleaching agent now in use for a conventional color image forming system and which accordingly minimizes the adverse effects on the environment has been reported on. For example, IS&T's 48.sup.th Annual conference Proceedings, p.180, discloses a system for carrying out a developing process without the use of a bleach-fixing bath, which has traditionally been indispensable in the conventional photographic process. The procedure comprises transferring the dye formed in the developing reaction to a mordant layer and thereafter stripping a light-sensitive material from an image receiving material bearing the mordant layer so that the developed silver and unreacted silver halide are removed. However, even this technique does not solve the environmental problems perfectly because the developing process still needs the processing bath.
Fuji Photo Film Co., Ltd. has proposed the Pictography System which dispenses with the need for a processing solution containing a color developing agent. In this Pictography System, the dyes formed in the development are fixed in the dye fixing layer. This is suitably used as a dye image for appreciation of images. This Pictography System comprises supplying a small amount of water to a light-sensitive material containing a base precursor and plying the light-sensitive material with an image receiving material and thereafter heating the materials to cause a developing reaction. This procedure does not use the aforementioned processing bath, and in this regard is advantageous with respect to the environment. It is possible to apply such a non-processing-solution-system to the processing of color photographic recording materials in order to solve the above problems.
However, when using high concentration silver chloride emulsions for colorphotographic light-sensitive materials to be heat-developed without the above processing solutions to enable rapid processing, various problems with the developing characteristics of the emulsions arise. Firstly, in order to get good graininess, it becomes necessary to inhibit the development of the grains which initiate the development while the process is still running. But when heat developable light-sensitive materials using high concentration silver chloride emulsions, it becomes difficult to inhibit the development because the rate of development is so high. As a result the graininess deteriorates. When the development is inhibited at a level where the graininess does not deteriorate, the development initiation timing of the light-sensitive grains becomes inconsistent, and it becomes more difficult to get a sensitive photographic response in the early stages of development. Secondly, fogging due to the high developability of the high concentration silver chloride emulsions, and the high temperature development becomes extremely high.
The combination of (100) plane, tabular silver chloride emulsion with the development inhibitor (mercaptotetrazoles, mercaptooxathiazol, benzotriazoles etc.) is outlined in the specification of WO94/22,054, noted above. However, nothing is mentioned in it about prevention of fogging in heat development.
The combination of (100) plane, tabular silver chloride emulsion with heat development is disclosed in Japanese Patent Application Publication (JP-B) No. 7-120014, but this disclosure concerns a method of image formation through the use of dye-providing chemicals. Mention of fogging resistance with regard to the light-sensitive materials used in the coupling reaction heat development is not made. Silver bromide and silver chlorobromide containing 80% silver bromide were given as examples. Fogging prevention due to concentrated silver chloride was not satisfactorily disclosed, and as a result, research into fogging prevention brought about by concentrated silver chloride emulsions of the light-sensitive materials presented in coupling reaction heat development has long been due.